chore(ngdocs): disable lunr search during e2e tests

lunr has been responsible for slowdown in our test suite by adding ~1sec per
end-to-end test.

(this is because it initializes the index when the app starts)

since out test suite primarily tests the examples, it's reasonable do disable
the search as a temporary meansure.

the real fix is to use protractor and extract all of the examples into
standalone apps which can be tested without bootstrapping the whole docs app.